How severe is CVE-2021-28141?

CVE-2021-28141 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-28141 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-28141?

CVE-2021-28141 affects Progress Telerik Ui For Asp.net Ajax. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-28141?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-28141 published?

CVE-2021-28141 was published on 2021-03-11 and last updated on 2026-06-17.

CVE-2021-28141

CVE-2021-28141 is a critical-severity vulnerability in Progress Telerik Ui For Asp.net Ajax with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-862.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (83rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-862
Affected product: Progress Telerik Ui For Asp.net Ajax
Published: 2021-03-11
Last modified: 2026-06-17

Description

An issue was discovered in Progress Telerik UI for ASP.NET AJAX 2021.1.224. It allows unauthorized access to MicrosoftAjax.js through the Telerik.Web.UI.WebResource.axd file. This may allow the attacker to gain unauthorized access to the server and execute code. To exploit, one must use the parameter _TSM_HiddenField_ and inject a command at the end of the URI. NOTE: the vendor states that this is not a vulnerability. The request's output does not indicate that a "true" command was executed on the server, and the request's output does not leak any private source code or data from the server

Frequently asked questions

What is CVE-2021-28141?: An issue was discovered in Progress Telerik UI for ASP.NET AJAX 2021.1.224. It allows unauthorized access to MicrosoftAjax.js through the Telerik.Web.UI.WebResource.axd file. This may allow the attacker to gain unauthorized access to the server and execute code. To exploit, one must use the parameter _TSM_HiddenField_ and inject a command at the end of the URI. NOTE: the vendor states that this is not a vulnerability. The request's output does not indicate that a "true" command was executed on the server, and the request's output does not leak any private source code or data from the server
How severe is CVE-2021-28141?: CVE-2021-28141 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-28141 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-28141?: CVE-2021-28141 affects Progress Telerik Ui For Asp.net Ajax. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-28141?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-28141 published?: CVE-2021-28141 was published on 2021-03-11 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:progress:telerik_ui_for_asp.net_ajax:2021.1.224:*:*:*:*:*:*:*

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